System and method for fan noise canceller

Abstract

A fan noise cancellation device comprises a base with a resonant ring formed with a plurality of resonance channels and a cover coupled to the base. Each resonance channel comprises an inner channel and an outer channel. Each inner channel has an opening to the resonant ring and has a length corresponding to a frequency. A baffle positioned in each inner channel determines an effective length of the inner channel. The inner channel baffles are coupled to the cover, wherein rotation of the cover relative to the resonance ring changes the position of the inner channel baffles to change the effective lengths of the inner channels to adjust the fan noise cancellation waveform frequency. Vanes on the cover are positioned in an airflow such that the airflow rotates the cover, and a spring in each resonance channel counteracts the rotation to adjust the inner channels.

What is claimed is: 
     
       1. A fan noise cancellation device comprising:
 a base comprising:
 a resonance ring; and 
 a plurality of resonance channels formed from a plurality of inner channels arranged around the resonance ring and a plurality of outer channels arranged around the plurality of inner channels, wherein each inner channel of the plurality of inner channels comprises an opening in the resonance ring; and 
 
 a cover coupled to the base, wherein 
 each inner channel of the plurality of inner channels is configured to generate a fan noise cancellation waveform at a corresponding opening based on an airflow passing through the fan noise cancellation device, and 
 the fan noise cancellation waveform has a frequency based on a length of a corresponding inner channel. 
 
     
     
       2. The fan noise cancellation device of  claim 1 , wherein:
 the cover comprises a plurality of inner channel baffles and a plurality of outer channel baffles; 
 each inner channel baffle is positioned in an inner channel of the plurality of inner channels; 
 an angular position of the inner channel baffle in the inner channel determines an effective length of the inner channel;
 the plurality of inner channels generate the fan noise cancellation waveform at a frequency based on the effective length of each inner channel; and 
 rotation of the cover relative to the base changes the angular position of the plurality of inner channel baffles in the plurality of inner channels to change the effective length of each inner channel. 
 
 
     
     
       3. The fan noise cancellation device of  claim 1 , wherein:
 the cover comprises a plurality of vanes, wherein airflow in contact with the plurality of vanes causes rotation of the cover relative to the base to change the angular position of the plurality of inner channel baffles in the plurality of inner channels; and 
 each outer channel of the plurality of outer channels comprises a spring, wherein each spring in the plurality of springs is configured to resist rotation of the cover. 
 
     
     
       4. The fan noise cancellation device of  claim 3 , wherein:
 the fan noise cancellation device is coupled to a fan configured to operate over a range of operating speeds, wherein each operating speed is associated with an airflow volume and a waveform frequency; and 
 one or more of the plurality of vanes, the plurality of springs, the overall length of each inner channel of the plurality of inner channels is configured to cause the plurality of inner channels to generate the fan noise cancellation waveform over the range of operating speeds. 
 
     
     
       5. The fan noise cancellation device of  claim 4 , wherein the range of operating speeds corresponds to a range of frequencies associated with a performance drop of a component in an information handling system. 
     
     
       6. The fan noise cancellation device of  claim 1 , wherein each inner channel comprises a length configured to generate a fan noise cancellation waveform corresponding to a blade passing tone (BPT). 
     
     
       7. A chassis for an information handling system, the chassis comprising:
 a plurality of components; 
 a fan for generating an airflow to cool the plurality of components, the fan generating a fan noise waveform; and 
 a fan noise cancellation device comprising:
 a base comprising:
 a resonance ring; and 
 a plurality of resonance channels formed from a plurality of inner channels arranged around the resonance ring and a plurality of outer channels arranged around the plurality of inner channels, wherein each inner channel of the plurality of inner channels comprises an opening in the resonance ring; and 
 
 a cover coupled to the base, wherein airflow through the resonance ring causes the plurality of inner channels to generate a fan noise cancellation waveform at the opening in each inner channel, wherein the fan noise cancellation waveform has a frequency based on a length of each inner channel. 
 
 
     
     
       8. The chassis of  claim 7 , wherein:
 the cover comprises a plurality of inner channel baffles and a plurality of outer channel baffles; 
 each inner channel baffle is positioned in an inner channel of a resonance channel of the plurality of resonance channels; 
 an angular position of the inner channel baffle in the inner channel determines an effective length of the inner channel;
 the plurality of inner channels generate a fan noise cancellation waveform at a frequency based on the effective length of each inner channel; and 
 rotation of the cover relative to the base changes the angular position of the plurality of inner channel baffles in the plurality of inner channels to change the effective length of each inner channel. 
 
 
     
     
       9. The chassis of  claim 7 , further comprising:
 a spring in each outer channel of the plurality of outer channels; and 
 a plurality of vanes coupled to the cover, wherein:
 airflow in contact with the plurality of vanes causes rotation of the cover relative to the base to change the angular position of the plurality of inner channel baffles in the plurality of inner channels; and 
 the spring is configured to resist rotation of the cover. 
 
 
     
     
       10. The chassis of  claim 9 , wherein one or more of the effective length of each inner channel, the opening in each inner channel, and the spring in each outer channel is configured to cause the plurality of inner channels to generate the fan noise cancellation waveform over a frequency range. 
     
     
       11. The chassis of  claim 9 , wherein the frequency range corresponds to a frequency associated with a performance drop of a component in the information handling system. 
     
     
       12. The chassis of  claim 7 , wherein each inner channel comprises a length configured to generate a fan noise cancellation waveform corresponding to a blade passing tone (BPT). 
     
     
       13. A method of manufacturing a fan noise cancellation device, the method comprising:
 forming a base comprising a resonance ring for allowing airflow to pass through the fan noise cancellation device; 
 forming a plurality of inner channels around the resonance ring, wherein each inner channel is formed with a length corresponding to a fan noise cancellation waveform frequency; 
 forming a plurality of openings on an inner surface of the resonance ring, wherein each inner channel of the plurality of inner channels is in fluid communication with the resonance ring via an opening of the plurality of openings; and 
 coupling a cover to the base, wherein airflow through the resonance ring causes the plurality of inner channels to generate a fan noise cancellation waveform at the fan noise cancellation waveform frequency. 
 
     
     
       14. The method of manufacturing a fan noise cancellation device of  claim 13 , wherein forming the plurality of inner channels around the resonance ring comprises forming each inner channel with a length corresponding to a blade passing tone (BPT). 
     
     
       15. The method of manufacturing a fan noise cancellation device of  claim 13 , wherein:
 forming the plurality of inner channels around the resonance ring comprises forming a plurality of inner channel baffles on the cover; 
 coupling the cover to the base comprises positioning each inner channel baffle in an inner channel of the plurality of inner channels such that an angular position of the inner channel baffle determines an effective length of the inner channel. 
 
     
     
       16. The method of manufacturing a fan noise cancellation device of  claim 15 , wherein:
 the cover is rotatably coupled to the base; and 
 rotating the cover relative to the base changes the angular position of the inner channel baffle in the inner channel to change the effective length of the inner channel. 
 
     
     
       17. The method of manufacturing a fan noise cancellation device of  claim 16 , further comprising:
 forming a plurality of outer channels around the plurality of inner channels; 
 positioning a plurality of springs in the plurality of outer channels; 
 forming a plurality of outer channel baffles on the cover, wherein each outer channel baffle is configured for contact with a spring of the plurality of springs; and 
 forming a plurality of vanes on the cover to generate a rotation force when in contact with an airflow, wherein
 coupling the cover to the base comprises:
 positioning each inner channel baffle in an inner channel of the plurality of inner channels such that an angular position of the inner channel baffle determines an effective length of the inner channel; and 
 positioning each outer channel baffle in an outer channel of the plurality of outer channels, wherein 
 airflow in contact with the plurality of vanes generates a first rotation force to rotate the cover relative to the base in a first direction to change the angular position of the plurality of inner channel baffles to decrease the effective length of each inner channel of the plurality of inner channels; and 
 contact between the plurality of outer channel baffles with the plurality of springs generates a second rotation force opposite the first rotation force to rotate the cover relative to the base in a second direction to change the angular position of the plurality of inner channel baffles to increase the effective length of each inner channel of the plurality of inner channels.